CNC laser machining devices including a combination of a laser oscillator and a numerical control (CNC) apparatus have come to be widely used. By combining high-speed machining provided by the laser machining device with complex contouring control achieved by the numerical control (CNC) apparatus, machining of a complex shape can be performed in a non-contact fashion and at high speed. Particularly, three-dimensional machining, which cannot be effected with a conventional punch press, nibbling machine or the like, can be achieved by three-dimensional shape machining laser devices which have been put to practical use. To carry out three-dimensional machining with the three-dimensional shape machining laser device, not only X, Y and Z axes but the pose of a nozzle arranged at a distal end portion of the device needs to be controlled. Usually, the nozzle is controlled in terms of .alpha. and .beta. axes. In the three-dimensional shape machining laser device, therefore, the .alpha. and .beta. axes in addition to the X, Y and Z axes must be controlled by means of machining commands.
However, in most cases, it is very hard to program such commands based on drawings. Therefore, geometric data of shape is usually collected while the distal end of the nozzle is positioned on an actual work, so that NC commands may be generated based on the data obtained. This process is accomplished through manual operation of teaching box by an operator.
In this teaching process, however, the nozzle is positioned on the work through manual operation, and, after the pose of the nozzle is controlled, a memory button is depressed so that the positions of the respective axes then assumed are used as NC commands. In consequence, precision of the NC commands obtained by the teaching i.e., precision of the teaching data, depends on positioning conditions of the nozzele and accordingly is not very high in general.
If an error produced in this process is so great that it cannot be absorbed by tracer control, the corresponding part of the work cannot be machined and is left unprocessed.